Electric generators, such as permanent magnet generators, are well known types of electrical power generating systems for supplying power to a wide variety of systems. A generator typically includes either a rotor mounted on a rotating shaft and disposed concentrically relative to a stationary stator or a stationary rotor positioned concentrically positioned within a rotating stator. An external energy source, such as a motor, an engine, or a turbine, commonly drives the rotating element. Both the stator and the rotor have a series of poles. The stator or the rotor generates a magnetic field which interacts with the windings on the poles of the other structure. As the magnetic field intercepts the windings, an electrical voltage is generated which is provided to a load. This voltage may also be applied to a bridge rectifier, sometimes regulated, and then provided as an output.
A permanent magnet generator uses permanent magnets to generate the required magnetic field. Permanent magnet generators are typically much lighter and smaller than traditional wound field generators. However, one disadvantage associated with a permanent magnet generator is that it is difficult to control or regulate the power supplied by the permanent magnet generator. For instance, the voltage supplied by the permanent magnet generator can vary significantly according to the speed of the rotor. Changes in the speed of the rotor can occur due to engine speed variations or changes in the load characteristics. Additionally, the voltage of a permanent magnet generator varies inversely with the current delivered. Stated another way, as the current increases the voltage decreases. Variations in the voltage are not acceptable for conventional loads and the voltage must be controlled or regulated.
Accordingly, the present invention is directed to overcome one or more of the problems as set forth above.